Mice homozygous for the Baxtm1Sjk mutation are viable but display lineage-specific aberrations in cell death. Thymocytes and B cells from homozygous mutant mice display hyperplasia. Ovaries contain unusual atretic follicles with excess granulosa cells while Bax-deficient males are infertile. There is an accumulation of atypical premeiotic germ cells and no mature haploid sperm found in seminiferous tubules. Multinucleated giant cells and dysplastic cells accompany massive cell death.
Used in conjunction with strain B6.129-Bak1tm1Thsn/J (see Stock No. 004183), to generate the double knock-out Bak/Bax, a model for demonstrating severe defects in the regulation of apoptosis during development and tissue homeostasis.
Coat color of Baxtm1Sjk mice
The coat color loci tyrosinase (Tyr) and pink-eyed dilution (p) are linked to the Bcl2-associated X protein (Bax) gene. According to backcross data from the Mouse Genome Database, Bax is at 23.00 cM, p is at 28.00 cM, and Tyr is at 44.00 cM on chromosome 7. The targeted disruption of the Bax gene was performed in a 129-derived RW-4 ES cell line (Aw/Aw p Tyrc-ch/p Tyrc) and was backcrossed 8 generations to C57BL/6 (a/a +p +Tyr-c/+p +Tyr-c; nonagouti black) before arriving at The Jackson Laboratory. The Jackson Laboratory's live colony of B6.129X1-Baxtm1Sjk/J mice (June 2019) is no longer segregating at the Tyr locus and do not retain the p allele from the 129 ES cell line: coat and eye color is black. However, the mice that were the source of the cryopreserved sperm (cryopreserved in 2003 at N12) may have been segregating at the Tyr locus and might retain the p allele from the 129 ES cell line. Thus, matings of Bax heterozygous (+/-) mice recovered from the cryorepository stock (N12 cryopreserved sperm) may produce progeny of varying coat color including black, white, chinchilla, light chinchilla, or grey, with all but the black mice having pink eyes. Because the potential for crossover between the p and Bax loci is small (roughly 5%), progeny from cryorecovered stock that are grey in color and have pink eyes most likely are homozygous for the targeted Bax gene (-/-).
